NASA’s Chandra Reveals Star’s Inner Conflict Before Explosion
The interior of a star turned on himself before he explodes spectacularly, according to a new study by the NASA X-ray observatory. Today, this broken star, known as the Cassiopeia, a supernova resides, is one of the best known and most studied objects in the sky.
More than three hundred years ago, however, it was a giant star on the verge of self -destruction. Chandra’s new study reveals that a few hours before its explosion, the interior of the star has violently rearranged. This last minute mixture of his stellar belly has deep implications to understand how the massive stars explode and how their leftovers behave later.
Cassiopeia A (case is to be short) was one of the first objects that the telescope examined after its launch in 1999, and astronomers returned several times to observe it.
“It seems that each time we look closely at the data from Chandra de Cas A, we learn something new and exciting,” said Toshiki Sato of the Meiji University in Japan who led the study. “Now we have taken this invaluable X -ray data, have combined them with powerful computer models and found something extraordinary.”
As massive stars are aging, the increasingly heavy elements are formed in their interiors by nuclear reactions, creating layers of onion of different elements. Their external layer is mainly made of hydrogen, followed by layers of helium, carbon and gradually heavier elements – extending to the center of the star.
Once Iron is starting to form at the heart of the star, the game changes. As soon as the iron nucleus grows beyond a certain mass (about 1.4 times the mass of the sun), it can no longer bear its own weight and collapses. The outer part of the star falls on the nucleus that collapses and bounces as a accelerated supernova.
The new research with Chandra’s data reveals a change that occurred deep in the star at the last moments of his life. After more than a million years, cases has undergone major changes in its last hours before exploding.
“Our research shows that just before the case of cases A has collapsed, part of an inner layer with large quantities of silicon went outwards and collapsed in a neighboring layer with a lot of neon,” said Kai Matsunaga co-author of the University of Kyoto in Japan. “This is a violent event where the barrier between these two layers disappears.”
This upheaval has not only brought back materials rich in silicon; He also forced material rich in neon to travel inward. The team has found clear traces of these exterior silicon flows and interior neon flows in the remains of the case supernova. The small regions rich in silicon but poor in neon are located near the regions rich in neon and silicon poor.
The survival of these regions provides not only critical evidence of the upheaval of the star, but also shows that a complete mixture of silicon and neon with other elements did not occur immediately before or after the explosion. This lack of mixture is predicted by detailed computer models of massive stars near the ends of their lives.
There are several significant implications for this interior turmoil inside the condemned star. First, it can directly explain the unbalanced form rather than symmetrical of the case a rest in three dimensions. Second, an unbalanced explosion and debris field may have given a powerful kick to the remaining kernel of the star, now a neutron star, explaining the high speed observed of this object.
Finally, strong turbulent flows created by the internal changes of the star may have favored the development of the blast supernova wave, facilitating the explosion of the star.
“Perhaps the most important effect of this change in the structure of the star is that he may have helped to trigger the explosion itself,” said co-author Hiroyuki Uchida, also from the University of Kyoto. “Such a final internal activity of a star can change her fate – whether or not she will shine like a supernova.”
These results were published in the latest issue of The Astrophysical Journal and are available online.
To find out more about Chandra, visit:
https://science.nasa.gov/chandra
Find out more about the Chandra’s radiography observatory and its mission here:
https://chandra.si.edu
This version has a composite image of Cassiopeia A, a Supernova resurge in the shape of a belly located around 11,000 light years from the earth. The image includes a close -up in inset, which highlights a region with relative abundances of silicon and neon.
More than three hundred years ago, Cassiopeia A, or case A, was a star on the verge of self -destruction. In composition, it looked like an onion with layers rich in different elements such as hydrogen, helium, carbon, silicon, sulfur, calcium and neon, wrapped around an iron core. When this iron core has become beyond a certain mass, the star could no longer bear its own weight. The outer layers fell into the collapsed nucleus, then rebounded like a supernova. This explosion created the form of donut indicated in the composite image. The shape is somewhat irregular, with the thinner quadrant of the donut at the top left of the off -center hole.
In the body of the donut, the remains of the elements of the star create a cloud of marbled colors, marbled with red and blue veins. Here, sulfur is represented by yellow, calcium by green and iron by purple. The red veins are silicon, and the blue veins, which also line the outer edge of the donut shape, are the highest energy rays detected by Chandra and show the breath wave of the explosion.
The insert uses a different color code and highlights a colored region and marbled with a thinner and higher left quadrant of cases A. Here, rich pockets of silicon and neon are identified in the red and blue veins, respectively. New evidence of Chandra indicate that in the hours preceding the collapse of the star, part of a layer rich in silicon traveled to the outside and burst into a neighboring layer rich in neon. This violent rupture of the layers has created solid turbulent flows and may have favored the development of the breathlessness wave of the supernova, facilitating the explosion of the star. In addition, upheavals inside the star may have produced an unbalanced explosion, causing the irregular shape, with a decentralized hole (and a thinner donut bite!) At the top left.
Megan Watzke
Chandra X X -ray center
Cambridge, mass.
617-496-7998
mwatzke@cfa.harvard.edu
Corinne Beckinger
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
Corinne.m.beckinger@nasa.gov
